This section provides background information related to the present disclosure which is not necessarily prior art.
Industrial control devices or controllers are used to control industrial operations. For example, servo drives can be used to control industrial machinery by providing appropriate drive signals to that machinery. Industrial controllers of this type must themselves be managed and controlled in order to provide the desired performance. This means controllers must have input/output (I/O) functionality.
Often, industrial controllers are used in concert, with specialised devices used for specific tasks. As an illustrative example, one may consider a 3D system in which there is a desire to control an element to take a position in 3D space. This requires control in all three dimensions. One approach would involve separate controllers for each of the three dimensions working together. The controllers in such a system must communicate with one another effectively in order to produce the desired result.
Typically, a backplane is provided to allow controllers within a system to communicate. A backplane provides a communications interface through which signals may be passed between controllers connected to the backplane. The backplane operates a given input/output (I/O) protocol which the controllers are designed to operate with through their own I/O componentry.
The I/O protocols operated by backplanes are often proprietary and designed by the supplier of the industrial controllers. This means there is a lack of interoperability between controllers provided by different manufacturers. Accordingly when it is desired to upgrade or repair a system comprising a plurality of controllers by adding or replacing a controller, any new controller must be adapted to work with the appropriate I/O protocol used by the backplane. Even if the protocol is not itself proprietary, there remains a requirement that all controllers operate the same I/O protocol and are able to physically interface with the backplane.
As a result of these issues, a given controller will only operate with compatible backplanes. Accordingly, an operator who wishes to obtain an appropriate controller has a choice limited to those that are compatible with the current systems, which can lead to sub-optimal choices.
The increasing complexity of control tasks has led to an increasing to desire to communicate with controllers through computer sources outside of the backplane. For example, it may be commercially desirable to effect control or monitor performance from a conventional computer or another part of a business system. However, the typical communications protocols used by business systems are again different to that used by industrial controllers. Often, business systems will communicate using Ethernet based protocols, for example. There has thus been a need for a bridging device or devices to communicate between the different protocols in use. This leads to further expense and potential issues of reliability.
An example of an approach to bridging between an Ethernet network and a protocol for use with industrial controllers is described in U.S. Pat. No. 8,203,980. Here a bridging system is disclosed in which a number of components connected to a backplane may be linked to an Ethernet general purpose network through a single node on the general purpose network. The purpose is to avoid each individual component on the backplane having to interface with the general purpose network directly. However, the components of the backplane are still obliged to communicate with each other using the appropriate protocol for the backplane itself.
In recent times, efforts have been made to develop an appropriate protocol for controller communication based on Ethernet. One example is the EtherCAT (Ethernet for Control Automation Technology) protocol, which is a high performance Ethernet-based protocol designed to offer short data update times and low communication jitter. This allows a more ready integration of the controllers and backplane with an Ethernet-based general purpose network.
There remain a range of communication protocols for backplanes used with industrial controllers and similar devices. While protocols based on Ethernet provide some standardisation, in the absence of an accepted universal standard, devices of this type continue to require specific componentry for each protocol with which they want to operate. This leads to a lack of customer choice, as they may for example be limited to devices which are interoperable with legacy systems.